1. Field of the Invention
The present invention relates to a heat exchanger such as a condenser, evaporator, or heater core used in an air-conditioning system for automotive or home use.
2. Description of the Related Art
One of the typical configurations of a condenser used for condensing and liquefying a refrigerant compressed by a compressor by air etc. in a conventional air-conditioning system is shown in FIG. 4 and in a partially cutaway enlarged view of FIG. 5. In a condenser 21 of the related art, a plurality of flat tubes 22 formed by extruding an aluminum material are arranged in parallel at predetermined intervals. First and second ends of these tubes are connected to common tubular headers 23 and 24. Corrugated fins 25 comprised of thin sheets of aluminum bent in a wave shape are attached sandwiched between adjoining flat tubes 22. Further, connection blocks 26, 27, etc. for connection of outlets and inlets of the refrigerant at the header 24 to not shown piping are provided. Note that these flat tubes 22 may also be formed with a large number of fine refrigerant passages 28.
While not shown, the header 24 is divided by a partition provided in the middle in the longitudinal direction into upper and lower parts communicating with the connection blocks 26 and 27, respectively. Therefore, the gaseous refrigerant compressed by a not shown compressor flows from the connection block 26 to the header 24, is distributed to the fine refrigerant passages 28 of the group of the over half of the flat tubes at the top among the plurality of flat tubes 22 in the top space from the not shown partition of the header 24, passes through the group of flat tubes 22 at the top, and flows into the other header 23. The refrigerant collected at the header 23 is distributed to the refrigerant passages 28 of the group of flat tubes 22 at the bottom, passes through them, then is collected at the bottom space from the not shown partition of the header 24 and returns from the connection block 27 to a not shown refrigeration cycle. The gaseous refrigerant is cooled by the flow of air through the spaces of the flat tubes 22 and the corrugated fins 25 while flowing through the fine refrigerant passages 28 of the flat tubes 22, so the majority of the refrigerant is condensed and liquefied to form a liquid refrigerant.
Even in a condenser 21 of the related art of this configuration, to promote heat exchange between the corrugated fins 25 and the flow of air, sometimes pieces of the corrugated fins 25 are cut and raised to form a large number of louvers 29 and sometimes the fins are embossed to form relief shapes to obtain so-called “wavy fins” (see Japanese Unexamined Patent Publication (Kokai) No. 2001-50678). The surfaces of the flat tubes, however, are smooth. Further, even at the corrugated fins 25, the parts 30 where the louvers 29 or relief shapes cannot be formed are smooth. Therefore, by just forming louvers 29, relief shapes, etc. at parts of the corrugated fins 25, the heat exchange efficiency between the outer surfaces of the flat tubes 22 and the flow of air at the outside of the tubes 22 is not improved much at all.